The overall goal of the program is to increase the quantity and biosecurity of mouse housing space in the Biomedical Research Building (BRB) vivarium at the University of Pennsylvania School of Medicine. BRB is the largest single component of the School's vivaria (27,000 NSF), and supports the research efforts of 49 faculty with more than $48 million in direct costs for biomedical research. The project goal is accomplished through two closely linked specific aims: (1) Improve barrier protection for mice by purchasing ventilated change stations for each animal housing room, and utilizing change stations both to protect mice during cage changing and during animal procedures/handling; and (2) To increase the housing capacity of the vivarium by 840 cages through conversion of shared procedure rooms into mouse housing rooms. Despite best practices, the BRB barrier facility has experienced 5 outbreaks of the infectious agents mouse hepatitis virus (MHV) and pinworms within the past 16 months. These outbreaks have had a devastating effect on the research activities of the faculty and resulted in euthanasia of numerous animals. During these events, MHV and pinworms have rapidly spread to multiple rooms within suites, and suggest that containment failure is linked to the design/use of the vivarium. Animal suites within BRB share a common procedure room and use ventilated cages without change stations; as a result, the spread of infectious agents can occur through either the opening of cages in the animal room on open carts and/or the use of shared procedure space. Our proposal is to supply change stations to each room, which may then also serve as handling stations for researchers, and to convert the common procedure room in 3 of 6 suites to dedicated housing units. Conversion of procedure rooms to housing will increase the capacity of the vivarium by 840 cages, which address a critical institutional need for expanded animal housing. The School engaged in a robust facility development plan over the past 12 years to match an extraordinary 231% increase in NIH funding. Despite this effort, the need for use of the mouse model in research, which grew by an astounding 239% in the past six years, was not fully met; the current facility census is in excess of 80% maximal capacity (>85% in BRB), and the faculty have identified an as yet unmet need for a 52% immediate increase in capacity. Thus, without the funds provided by this grant we will significantly impede ongoing biomedical research at the School, and dramatically restrict program development.